Improved thermoplastic condensate polymers and method to form them

ABSTRACT

Copolymers of condensation polymers are formed by a method of cleaving and reacting with a chain extender to form an end capped cleaved condensation polymer that is further reacted with a second compound that may be comprised of a further chain extender and condensation polymer that react with a reactive group still remaining in the chain extender capping the cleaved condensation polymer. The method allows the formation of block copolymers, branched copolymers and star polymers of differing condensation polymers bonded through the residue of a chain extender.

FIELD

The invention relates to condensate polymers and method to make them. In particular, the invention relates to cleaving of polycondensate polymers (e.g., polyamides and polyesters), capping of the cleaved polymers with a multifunctional end cap and reacting the multifunctional end cap with another compound that can undergo condensation.

BACKGROUND

Condensation polymers have been used to form shaped articles by traditional methods such as extrusion, film blowing, injection molding and the like. In these processes, the polymer is melted and substantially sheared resulting in cleaving of the polymer and uncontrolled loss of molecular weight causing deformation during forming of the shape (e.g., blow molded bottes and extruded tubes). Typically, a chain extender is added to reconstitute the molecular weight loss to realize sufficiently high melt strength and melt viscosity as described for polyester and polyethylene terephthalate in U.S. Pat. Nos. 4,246,378 and 7,544,387 respectively.

Additive manufacturing of thermoplastic polymers typically requires localized melting in layered patterns that then fuses and supports subsequent layers. Fused filament fabrication (FFF), which is also commonly called plastic jetprinting has been used to form 3d parts by using thermo plastic filaments that are drawn into a nozzle heated, melted and then extruded where the extruded filaments fuse together upon cooling (see, for example, U.S. Pat. Nos. 5,121,329 and 5,503,785).

Likewise, selective laser sintering or melting (SLS or SLM) has been used to make 3d parts by selectively sintering powders in a bed of powder (see, for example, U.S. Pat. No. 5,597,589). In this method, a bed of powder maintained at elevated temperatures is selectively sintered using a CO₂ laser or other electromagnetic radiation source. Once a first layer has been sintered, a further layer of powder is metered out and the selective sintering repeated until the desired 3d part is made. Since the powder must be sintered or melted, SLS has been limited to the use of thermoplastic polymers with very particular characteristics to allow for sintering without warping, slumping and achieving desired fusing particularly between layers. These requirements have tended to require the use a single type of polymer or highly compatible polymers when printing.

Because of the local heating and the need for the part being made to support itself as it is being formed, the strength of the bonding within a layer and in particular between layers is typically lower than a part formed from a monolithic molded mass (e.g., injection molded). Because of the constraints dictated by the ability to localize heat, melt and regain sufficient strength to support the part being formed, the strength within a layer and between layers (referred to as strength in the Z direction or build direction) have been problematic in the use varying polymer together homogeneously within the part or heterogeneously in the part.

Accordingly, it would be desirable to provide condensation polymers that solves one or more of the problems in the art, such as allowing for the use of condensation polymer with limited compatibility to make additive manufactured articles or other shaped articles.

SUMMARY

It has been discovered that by the selection of particular chain extenders, condensation polymers and processing unique condensation block copolymers, branched and star copolymers may be formed. These in turn may be used as compatibilizers with homopolymers of the blocks of the block copolymers of this invention. They may also be used to form articles by additive manufacturing methods, blow molding, injection molding and the like.

A first aspect of the invention is a method of forming a chain extended condensation polymer comprising: (i) heating a condensation polymer in the presence of multifunctional chain extender to cause a portion of the condensation polymer to be cleaved to form a cleaved polymer having a cleaved end, wherein the chain extender reacts with at least a portion of the cleaved ends to form an end capped cleaved polycondensate polymer having an end cap that has at least one condensation reactive group, (ii) reacting a second compound having a reactive group that reacts with the end cap reactive group of the cleaved condensation polymer to form the chain extended condensation polymer, the second compound being different than the condensation polymer. In a particular embodiment, the chain extender has a functionality of 1 (i.e., acts as an end cap for the capped cleaved polycondensate polymer), but the same chain extender has a functionality of 2 with another condensation polymer that can then react with the reactive functionality remaining in the chain extender capping the cleaved end capped condensation polymer.

A second aspect of the invention is a block copolymer comprising a plurality of blocks and each block is a condensation polymer that is attached to another block through the residue of a chain extender with at least two blocks being chemically different.

A third aspect of the invention is a branched block copolymer comprising, a plurality of blocks, each block being a condensation polymer and each block and branch is attached through the residue of a chain extender with at least one block or one branch being different than another branch or block of the branched block copolymer.

A fourth aspect of the invention is a star condensation copolymer comprising a plurality of legs, wherein each leg is a condensation polymer that is attached through the residue of a chain extender with at least one leg being chemically different than another leg of the star copolymer.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the method to form a linear copolymer of the invention.

FIG. 2 is an illustration of the method to form a star copolymer of this invention.

FIG. 3 is another illustration of the method to form a star copolymer of this invention.

FIG. 4 is an illustration of the method to form a branched copolymer of this invention.

DETAILED DESCRIPTION

The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. The specific embodiments of the present disclosure as set forth are not intended to be exhaustive or limit the scope of the disclosure.

One or more as used herein means that at least one, or more than one, of the recited components may be used as disclosed. It is understood that the functionality of any ingredient or component may be an average functionality due to imperfections in raw materials, incomplete conversion of the reactants and formation of by-products.

The method of the invention involves heating a condensation polymer sufficiently to cleave a portion of said polymer in the presence of a multifunctional chain extender. The chain extender reacts with the cleaved end. The multifunctional chain extender then reacts with a different second compound to form the chain extended polymer of this invention, which may be a block, graft or star polymer having one or more differing blocks. The method may be facilitated by shearing the condensation polymer.

The condensation polymer may be any suitable condensation polymer such as those known in the art and commercially available. Examples of useful polymers include a polyamide, polyester, polycarbonate, polyamideimide, polyimide, polyacetal or combination thereof. Desirably, the polymer is a polyamide, polyester, or polycarbonate. The condensation polymer may be linear or branched. Desirably, the condensation polymer is linear. Examples of polyamides include those available from Ube Industries Ltd., such as types Polyamide 6, Co polyamide (6/66), Co-polyamide (6/66/12), and Co-polyamide (6/12). Examples of polyesters include polyethylene terephthalate and other commercial polyesters such as those available from Celanese under the tradename CELANEX. Examples of polycarbonate include those available from Trinseo S.A. under the tradename CALIBRE.

Typically, the condensation polymers have a weight average molecular weight (Mw) of greater than 1000, 10,000, 100,000 to 1,000,000 daltons. Typically, the condensation polymers have a melt flow rate (MFR) measured: [g/10 min.] 2.16 Kg @235° C. by a method prescribed by ASTM D1238 of 0.1 or 1 to 100, 50, 20 or 10.

The multifunctional chain extender may have differing functionality depending on the particular condensation polymer used. Desirably, the functionality of the chain extender is from 1 or 2 to 5 with at least one of the condensation polymers and at least 2 to 4 with the second compound to realize the desired chain extension to for the chain extended condensation polymer. In a particular embodiment, the chain extender has a functionality of 1 (acts as an end cap) for the condensation polymer and a functionality of 2 or more with the second compounds (i.e., extends the condensation polymer with the second compound), which is further illustrated herein. As an illustration of a particular embodiment, the anhydrides, which are particularly useful for end capping polyamides (functionality of 1), which is described in co-pending application filed concurrently having a title, CHAIN SCISSION TO MAKE IMPROVED POLYMERS FOR 3D PRINTING by Thomas Fry, et. al., incorporated herein by reference, may react with polyesters twice (functionality of 2). Likewise, the chain extender may have 2 or more functional (reactive) groups with differing reactivity with a particular condensation polymer or differing reactivity with differing condensation polymers.

The chain extender may be any useful for reacting and extending the condensation polymer and may vary depending on the particular condensation polymer. Examples of chain extender include those that are comprised of an epoxide, carboxylic acid, alcohol, anhydride, amines, isocyanate, aziridine, oxazoline, or phosphite ester or any combination thereof. Desirably, the chain extender is comprised of a carboxylic acid, epoxide, anhydride or any combination thereof.

It is understood that the chain extender may have the ability to react with differing condensation polymers two or more times to extend the particular condensation polymer and or may be able to connect differing condensation polymers during the method. One or more multifunctional chain extender may be used, for example, to realize differing desired structures of the resulting chain extended condensation polymer. As an illustration a small quantity of a higher functionality (e.g., 4-10 reactive groups) chain extender may be used with a large quantity of 2 functionality chain extender to realize structures such as a star polymer.

Examples of epoxides may include solid epoxy resins such as those available under the tradename EPON from Miller-Stephenson and styrene based epoxide containing compounds available under the tradename JONCRYL from BASF. Other examples include epoxy thermoplastic elastomers. Additional examples include (poly) ethylene glycol diglycidylether, (poly)propylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, resorcin diglycidyl ether, neopentylglycol diglycidyl ether, 1,6-hexanediol diglycidylether, diglycidyl adipate, diglycidyl o-phthalate, diglycidyl terephthalate, hydroquinone diglycidyl ether, bisphenol S diglycidyl ether, glycerol diglycidyl ether, Sorbitol polyglycidyl ether, Sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerolpolyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanurate, glycerol triglycidyl ether, and trimethylolpropanepolyglycidyl ether. Another additional epoxy compound is epoxidized soybean oil.

Examples anhydrides may include pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, butane-1,2,3,4-tetracarboxylic dianhydride, maleic anhydride homopolymers, maleic anhydride-vinyl acetate copolymers, maleic anhydride-ethylene copolymers, maleic anhydride-isobutylene copolymers, maleic anhydride-isobutyl vinyl ether copolymers, maleic anhydride-acrylonitrile copolymers, maleic anhydride-styrene copolymers, tetrabromophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, 1,8-naphthalic anhydride, phthalic anhydride, or sulfophthalic anhydride, phenylenebisoxazoline, trimellitic dianhydride pyromellitic dianhydride, Bisphenol A-diglycidyl ether tetraepoxide tetraglycidyldiaminodiphenyl methane.

Exemplars of other chain extenders that may be useful, include those described in U.S. Pat. No. 7,544,387 from col. 3, line 10 to col. 5, line 34, incorporated herein by reference.

Illustrations of chain extenders displaying a functionality of 1 for polyamide and functionality of 2 for polyester include anhydrides having only one anhydride such as, but not limited to, phthalic anhydride, tetrabromophthalic anhydride, hexahydrophthalic anhydride, sulfophthalic anhydride, trimellitic anhydride, 1,8-naphthalic anhydride. Illustratively, the anhydride can ring open the anhydride leaving a carboxylic acid that can then be reacted with a polyester forming a chain extended block copolymer. Illustrations of further multifunctional chain extenders are described in co-pending application filed concurrently having a title, METHOD FOR IMPROVING ADHESION IN AND BETWEEN LAYERS OF ADDITIVE MANUFACTURED ARTICLES, by Thomas Fry, et. al., incorporated herein by reference.

The condensation polymer and chain extender are heated and sheared sufficiently to cleave at least a portion of the condensation and have the chain extender react with the cleaved end to form the end capped cleaved condensation polymer. It is understood that the chain extender may react with terminal groups of the condensation polymer too and to cause some chain extension of the condensation polymer itself, so long as there is a portion of such end capped cleaved condensation polymer has an end cap having at least one further condensation reactive group that may react with the second compound. A portion may be any amount to realize the desired end capped cleaved condensation polymer and chain extended condensation polymer. Typically, a portion may be any amount from about 2 to 3, 10, 20, 50, 75 percent by number or weight to essentially all, with it being understood that all of the condensation polymer may be cleaved, end capped and extended.

The second compound may be any desired compound to be incorporated into the condensation polymer of this invention. For example, the second compound may be a compound that may react with one or more functional groups remaining in the residue of the chain extender capping the cleaved condensation polymer. Examples of the second compound may be other condensation polymers that are chemically different than the condensation polymer, which has been reacted with the chain extender. These second compounds of condensation polymers may be any of those described previously. The second compound may be an oligomer that is formed from a condensation reaction and has one or more chemical groups that may react with the chain extender reacted with the condensation polymer. The second compound may be a compound such as another chain extender that can react with the chain extender reacted with the condensation polymer adding further functionality to the condensation polymer reacted with the chain extender (in such cases, further extension may be subsequently by adding a further different second compound such as another condensation polymer).

The heating to form the end capped cleaved condensation polymer may be any suitable method and apparatus for heating and mixing/shearing polymers such as those known in the art. Examples include high intensity mixers and screw extruders (e.g., single and twin screw extruders). The amount of shear may be any useful to facilitate the cleaving and end capping desired in a particular apparatus. The extruder may be held at one temperature or have a gradient along the length of the extruder to facilitate the cleaving and end capping desired. The temperature may be any that is sufficient to form the end capped cleaved condensation polymer, for example, just below the temperature where a particular condensation polymer starts to degrade. Typically the temperature may be a temperature that is 100° C., 50° C., or 25° C. within the melting temperature of the condensation polymer. Typical temperatures may be from about 150° C., 175° C., or 200° C. to about 300° C. or 250° C. Likewise, when reacting the second compound any temperature may be used to form the chain extended condensation polymer such as those just described. The shear may be any as typically used in the practice of compounding condensation polymers in compounding extruders. The time likewise may be any time sufficient to realize the desired chain extended condensation polymer. Typical times may be from 1 to 2 minutes to several hours (3-5) for reacting the chain extender with the cleaved condensation polymer or reacting with the second compound.

FIG. 1 illustrates one embodiment of forming a linear block copolymer made by the method of this invention. In this illustration, Polyamide 1A is cleaved and forms polyamides PA1A and PA1B with PA1B being end capped by the chain extender (trimellitic anhydride depicted). These two new polyamides (PA1A and PA1B) of reduced molecular weight may form a linear block copolymer of alternating blocks of the initial two polyamides (PA1A and PA1B) by using a chain extender second compound (e.g., pyromellitic dianhydride). A branched or star block polymer may also be formed as described below. It is understood that the PA1A may be a separately provide polyamide of differing chemistry or structure. In other embodiments, two polymers of different types can be combined by selection of the appropriate end capping reactant and chain extender. This type of copolymerization can take place between any polycondensate pair provided, such as: polyamide/polyester, polyamide/polyimide, polyester/polycarbonate, and other combinations thereof with the appropriate chain extender and second compound, which may include a further chain extender and condensation polymer. Thus, the method may form novel and unique block copolymers comprised of a condensation polymer block that is attached to another block through the residue of a chain extender with at least two blocks being chemically different such as those condensation polymer pairs described above. In a particular embodiment, the block copolymer has an alternating A-B block structure (e.g., A-B-A or A-B-A-B-A). Desirably the A block is a polyamide and B block is polyester. The block copolymer may be any useful Mw. The block copolymer may be useful as compatibilizer and, in a particular embodiment, the block copolymer may be an insitu produced compatibilizer for unreacted condensation polymers remaining during the process of forming the block copolymer.

FIG. 2 illustrates the formation of a star polymer. In this illustration, the polyamide in the illustration described above is heated and sheared in combination with a second compound comprised of a further chain extender pyromellitic dianhydride and a polyester as shown, which then forms a star polymer having three legs with one leg being polyamide and 2 legs being polyester. Thus, the method may form novel unique star polymers comprising a plurality of legs, wherein each leg is a condensation polymer that is attached through the residue of a chain extender with at least one leg being chemically different than another leg of the star copolymer. Desirably, each leg of the star polymer has a molecular weight that is within 30% of the number average molecular weight (Mn) of all the legs. Desirably, the star copolymer legs are comprised of a condensation polymer selected from the group consisting of polyamide, polyester, polycarbonate, polyamideimide, polyimide, or polyacetal. In a particular embodiment, at least one of the legs is a polyamide or polyester. Exemplary condensation polymer pairs that may make up the legs may be the same as those described above for the linear block copolymers.

FIG. 3 , illustrates a further route to make a star polymer, which may then be used as a cross-linker. FIG. 3 shows a polyamide that has been cleaved using aminophthalic anhydride. The two new polyamides of reduced molecular weight can be combined in the extrusion process by using a chain extender such as mellitic anhydride. Because most chains contain terminal amino groups, the primary reaction with the mellitic anhydride can be three functional. In this case, the three anhydrides are opened to bond with these terminal amino groups. Three free polyamide chains are able to be bound at this junction creating a large star like molecule. At the end of these three chains, a similar reaction can take place with additional chain extenders, resulting in a crosslinked system.

FIGS. 4A and 4B, illustrates the formation of branch copolymer by the method of the invention. FIGS. 4A and 4B displays a reaction scheme for two different linear polyamides being used to develop one branched polyamide. In this scheme, Polyamide 1A refers to a polyamide of high molecular weight whereas Polyamide 2 is considered to be of low molecular weight. In two separate extrusion processes, these polyamides are cleaved and end capped using aminophthalic anhydride and hydroxyphthalic anhydride, respectively. In a third extrusion, polyamides 1A and 1B are melt processed with dihydroxypyromellitic dianhydride resulting in a chain extension reaction between the amino end caps of the two polymers and the counter facing anhydride groups present on the chain extension molecule. The resulting polymer can then be melt processed with a chain extender like bisphenol-A diglycidyl ether (DGEBA) and polyamides 2A and 2B to encourage a second chain extension reaction. In this reaction, the epoxy groups on the chain extending molecule can form a covalent bond with the hydroxyl groups present on the dihydroxypyromellitic dianhydride. The remaining hydroxyl group from the DGEBA can then link with the hydroxyl and amino ends of polyamides 2A and 2B to form branches off the longer main polymer chain.

The copolymerization and branching may allow the crystallization kinetics to be tuned. In the examples above where block copolymers are created, crystallization can be controlled by the ratio and selection of the two polymers used. In a hypothetical case where two polyamides are of differing glass transition temperatures are shortened and end capped, the combination of the two constituents with the appropriate chain extender can produce a polyamide with adjusted thermal properties. Slow crystallizing segments, such as those derived from a polyamide 12, can be bound to segments from a polyamide 6 to retard crystallization. High temperature polyamides sections, such as polyphthalamide, can be bound to segments of lower temperature polymamides, such as nylon 6, to modify the glass transition and melting temperatures through co-crystallization and steric hindrance. Additionally, traditionally amorphous polymer sections, such as those from glycol modified polyethylene terephthalate, can be bound to a polyamide to slow or completely disrupt crystal growth.

In other embodiments, branching can be used to slow crystallization to a controlled extent. Using the example presented in FIGS. 4A and 4B, the length and amount of chains from polyamide 2A and 2B can be used to slow crystallization and decrease the degree of crystallinity. By increasing the number of branches and length of those branches along the backbone created by the chain extension of polyamide 1A and 1B, the free volume between chains can be increased. This increased free volume can disrupt crystal formation by preventing packing of the polyamide chains as well as by inhibiting the ability for the chain to reorient. This adjustment of crystallization can be highly controllable based on the selection of polymers to be placed in the backbone/branches as well as the concentration of chain extending molecule chosen to enable branching.

The degree of crystallization for a given condensation polymer that is made into a branch or star polymer may be changed by about 10%, 20%, 30% 50% or more with all other things being essentially equal such as Mw, polydispersity, heating and cooling history. For example, a linear polyamide that is cleaved and formed into a branched polymer from the cleaved segments may realize such a change in degree of crystallization. Likewise, the rheological properties may also vary by such amounts, for example, the MFR, as described herein may vary in a like manner. 

1. A method of forming a chain extended condensation polymer comprising: (i) heating a condensation polymer to within 50° C. of its melting temperature under and in the presence of multifunctional chain extender to cause a portion of the condensation polymer to be cleaved to form a cleaved polymer having a cleaved end, wherein the chain extender reacts with at least a portion of the cleaved ends to form an end capped cleaved condensation polymer having an end cap that has at least one condensation reactive group, (ii) reacting a second compound having a reactive group that reacts with the end cap reactive group of the cleaved condensation polymer to form the chain extended condensation polymer, the second compound being different than the condensation polymer.
 2. The method of claim 1, wherein the multifunctional chain extender is comprised at least two functional groups comprised of epoxides, carboxylic acids, alcohols, anhydrides, amines, isocyanates, aziridines, oxazolines, phoshite esters, or combination thereof.
 3. The method of claim 1, wherein the chain extender has about 2 to about 10 carboxylic acid moieties.
 4. The method of claim 1, wherein the chain extender has at least two functional groups having different reactivity.
 5. The method of claim 4, wherein the chain extender functional group is a carboxylic acid, epoxide, or anhydride.
 6. The method of claim, wherein the functional group of the chain extender is comprised of an anhydride.
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled)
 11. (canceled)
 12. The method of claim 1, wherein the end cap has at least 2 to 5 reactive groups.
 13. (canceled)
 14. A block copolymer comprising a plurality of blocks and each block is a condensation polymer that is attached to another block through the residue of a chain extender with at least two blocks being chemically different.
 15. The block copolymer of claim 14, wherein the blocks are selected from the group consisting of polyamide, polyester, polycarbonate, polyamideimide, polyimide, or polyacetal.
 16. The block copolymer either claim 15, wherein at least one block is the polyamide and at least one block is the polyester.
 17. (canceled)
 18. (canceled)
 19. (canceled)
 20. The block copolymer of claim 14, wherein the block copolymer has an A block and a B block having an A-B-A or A-B-A-B-A block structure.
 21. The block copolymer of claim 20, wherein the A block is a polyester or polyamide and the B block is a polyester or polyamide.
 22. The block of copolymer of claim 14, wherein the block copolymer is a compatibilizer.
 23. A branched block copolymer comprising, a plurality of blocks, each block being a condensation polymer and each block and branch is attached through the residue of a chain extender with at least one block or one branch being different than another branch or block of the branched block copolymer.
 24. The branched block copolymer of claim 23, wherein the blocks and branches are polyamide, polyester, polycarbonate, polyamideimide, polyimide, or polyacetal.
 25. The branched block copolymer of claim 24, wherein at least one block or branch is the polyamide.
 26. The branched block copolymer of claim 25, wherein at least one block or branch is a polyester.
 27. The branched block copolymer of claim 23, wherein the chain extender is comprised of the residue of at least two functional groups comprised of epoxides, carboxylic acids, alcohols, anhydrides, amines, isocyanates, aziridines, oxazolines, phoshite esters, or combination thereof.
 28. The branched block copolymer of claim 27, wherein the chain extender functional group is a carboxylic acid, epoxide, or anhydride.
 29. The branched block copolymer of claim 23, wherein the branched block copolymer has one or more rheological properties that is different by at least about 10% compared to a linear condensation polymer comprised of the same chemical and essentially same molecular weight and polydispersity. 30-37. (canceled) 